Tea is made from the tea plant Camellia sinensis. There are four major categories of tea: white, green, oolong and black. The categories refer to how much a tea is oxidized. Oxidation is the natural process that changes the color and flavor of the tea leaf as it is exposed to air. White tea is one of the most delicate tea varieties because it is minimally processed. White tea is harvested before the tea plant's leaves open fully, when the young buds are still covered by fine white hairs, hence the name "white" tea.